1. Field of the Invention
The invention relates to a device for removing externally a fluid substance soiling an endlessly wound conveyor belt driven around at least two end rollers, at least one of which is motor-driven. In particular the device is intended to clean conveyor belts of machines and plants for painting, dyeing or soaking processes, which below are referred to in short and for the sake of simplicity as “painting processes”, where the articles to be treated are conveyed through a chamber for spraying the fluid treatment substance such as a paint. The conveyor belt is formed by two sections: an upper outward section, usually carrying the articles to be treated which are coated with the paint spray as they pass through the spraying chamber, and a lower return section which is usually situated outside the said spraying chamber and which, emerging from said chamber, is soiled with paint which must be recovered so that the said conveyor may return clean to the upper section in order to receive new articles to be treated.
2. Description of Related Art
The devices currently used for recovery of the residual paint and for cleaning the belt comprise means for removing the paint from the belt itself with a skimming or scraping operation and comprise cleaning systems which wet the belt with solvent and then dry and clean it, for example using fixed doctor blades or rotating cylinders or a combination of these means. In European Patent No. 425,969 which is in the name of the Applicant the cleaning device comprises a cylinder or roller which operates along the return section of the conveyor belt with a parallel arrangement for example situated opposite the end transmission roller of the conveyor and this roller is rotated in the opposite direction to the direction of feeding of the belt to be cleaned, so as to perform effectively scraping-off of the residual paint, which is separated from this roller by cleaning means through the action of at least one doctor blade and falls into a collection and removal chute by means of gravity. The said counter-rotating cleaning roller, also called reverse roller, may be partially immersed with a bottom part thereof, inside a tank containing solvent so as to be completely or partially cleaned and convey a film of the said solvent into the zone of contact with the bottom section of the belt to be cleaned, in order to wet the belt zone from which the paint is removed and ensure that the same section of the conveyor leaves the reverse roller with an amount of solvent which has the function of softening further the residual paint which thus may be more easily removed by following cleaning means comprising a further reverse roller and/or fixed doctor blades and/or rotating brushes and any other suitable means. This reverse-roller cleaning system over time has proved to be very effective and advantageous, but has limitations due to the difficulty of removing rapidly the paint discharged by the cleaning blade of the reverse roller, without requiring the use of solvent and without the formation of lumps. In an attempt to solve these problems, various solutions have been attempted, one of which consists for example in mounting the cleaning blade along the longitudinal edge of a straight channel inside which the paint is collected and then pushed out from the ends of this channel by the alternating movement, inside the latter, of a scraping knife. Another solution, which is described for example in European Patent No. 1,964,795 in the name of the same Applicant, envisages using instead of the doctor blade, the longitudinal portion of the upper section of a motor-driven conveyor which performs simultaneously both the function of a doctor blade and means for rapid removal of the paint detached from the reverse roller. The first of the said solutions has the drawback that the action of the said scraping knife tends to cause stressing of the paint and the formation of lumps such that the paint cannot be easily reused. At the end of the working shift or when it is required to change the paint product and it is required to clean the paint recovery means, cleaning of said channel and the scraping spatula which operates inside it is not easy and requires a long time. The second of said solutions has a high cost and poses design-related problems with regard to ensuring uniformly distributed contact between the bottom cleaning conveyor and the reverse roller and is difficult to manage also owing to the need to ensure proper cleaning of the said bottom conveyor.